1. Field of the Invention
The invention relates generally to authentication marks or security marks and, more particularly, to a composite authentication mark having a bar code that is visible when illuminated with visible light and an infrared code that is visible when illuminated with infrared light but not visible when illuminated with visible light, and a device and method for reading the same.
2. Description of the Related Art
Various techniques have been used to identify articles in an effort to reduce counterfeiting. For collectibles such as art works and sports memorabilia, where a single item may be worth millions of dollars, a technique that is highly refined and virtually impossible to copy is desired. This is because high potential counterfeiting gains will motivate counterfeiters to invest large sums of money and resources to defeat the anti-counterfeit measure. Similarly, the high cost of implementing an anti-counterfeit measure for collectibles is typically accepted by the owner or insurer, because the potential loss from counterfeiting is great.
On the other hand, for mass produced items such as apparel, CDs, and audio and video cassettes, cost is a more important factor in implementing an anti-counterfeit measure. The implementation cost must be small enough so that the cost of the protected product will not increase dramatically. Yet, the anti-counterfeit measure must be refined enough so that counterfeiters will be unable to defeat the anti-counterfeit measure in a sufficiently easy manner such that they will be able to economically produce and sell counterfeit goods.
Mass produced items also have to be protected against product diversion. Product diversion occurs when a counterfeiter acquires genuine, non-counterfeit goods that are targeted for one market and sells them in a different market. The counterfeiter does this to circumvent the manufacturer""s goal of controlling the supply of his or her goods in a particular market and, as a consequence, benefits from the sales in that limited supply market or in the diverted sales market.
In one type of anti-counterfeit and anti-diversion measure, an ultraviolet (UV) ink is used to mark the product with an identifying indicia. One benefit of using the UV ink is that it is typically not visible when illuminated with light in the visible spectrum (380-770 nm), but is visible when illuminated with light in the UV spectrum (200-380 nm). Therefore, counterfeiters will be unable to tell whether the product contains a security mark by merely looking at the product when the product is illuminated with visible light.
A number of UV inks are readily available in the security industry and can be obtained at a relatively low cost. Several UV ink types and compositions are described, for example, in U.S. Pat. No. 5,569,317, entitled xe2x80x9cFluorescent and Phosphorescent Tagged Ink for Indiciaxe2x80x9d the disclosure of which is incorporated by reference herein. This patent discloses a security mark that becomes visible when illuminated with UV light having a wavelength of 254 nm.
However, the use of security marks containing a UV ink has seen increased use and counterfeiters have become knowledgeable about their use. It has been a common practice for counterfeiters to examine the UV ink from a product sample, reproduce or procure the same or similar UV ink that matches the characteristics of the UV ink from the product sample, and apply the same security mark on the counterfeit products using the substitute UV ink.
In another type of anti-counterfeit and anti-diversion measure, an infrared (IR) ink is used to mark the product with an identifying indicia. As with the UV ink, one benefit of using the IR ink is that it is typically not visible when illuminated with light in the visible spectrum, but is visible when illuminated with light in the IR spectrum (800-1600 nm). An additional benefit of using the IR ink is that it is more difficult to reproduce or procure the matching IR ink by studying a product sample containing the IR security mark. Examples of IR security mark usage are given in U.S. Pat. Nos. 5,611,958 and 5,766,324, the disclosures of which are incorporated by reference herein.
Combination security marks have also been proposed. In U.S. Pat. Nos. 5,360,628 and 5,599,578, the disclosures of which are incorporated by reference herein, a security mark comprising a visible component and an invisible component made up of a combination of a UV dye and a biologic marker, or a combination of an IR dye and a biologic marker is proposed. Also, in U.S. Pat. No. 5,698,397, the disclosure of which is incorporated by reference herein, a security mark containing two different types of up-converting phosphors is proposed.
Combination bar codes have also been proposed in U.S. Pat. Nos. 5,502,304 and 5,542,971, the disclosures of which are incorporated by reference herein. These patents describe a combination bar code having visible and UV bar codes overlaid one on another and a system for illuminating and reading the same. U.S. Pat. No. 5,766,324 also discloses a combination bar code having visible and IR bar codes overlaid partially one on another.
In the combination bar codes described above, the process for printing the mark must be performed in two separate stepsxe2x80x94a first step for printing the visible bar code and a second step for printing the invisible bar code. A single-step printing process cannot be used because the bars of the visible bar code overlaps the bars of the invisible bar code. In the same manner, the process for reading the mark is carried out in two separate stepsxe2x80x94a first step for reading the visible bar code and a second step for reading the invisible bar code.
An object of this invention is to provide a composite authentication mark comprising a bar code portion that is visible when illuminated with visible light and an invisible code portion that is not visible when illuminated with visible light, wherein the bar code portion includes a plurality of bars and spaces and the invisible code portion is arranged in at least one of the spaces of the bar code portion without overlapping any of the bars of the bar code portion. Because the invisible code portion does not overlap with any of the bars of the bar code portion, a single-step printing and reading processes may be used. As an additional benefit, because the invisible code portion is arranged in one or more spaces of the bar code portion, the visible ink used to print the bars of the visible bar code portion does not interfere with the reading of the invisible bar code portion by absorbing the light that is used to illuminate and excite the invisible code portion.
The invisible code portion of the authentication mark according to the invention is an IR code. A UV code may be used, but the IR code is preferred more, because a comparable IR ink to duplicate the characteristics of the IR code is more difficult to procure and the IR code cannot be located with a diffuse light source.
Another object of the invention is to provide a composite authentication mark including a visible bar code having bars and spaces and an invisible code portion arranged within at least one of the spaces, wherein the particular location or locations of the invisible code portion within the spaces are used in decoding the authentication mark. With this arrangement, more information can be compressed into the authentication mark.
Still another object of the invention is to provide a bar code reading system that decodes an authentication mark including both a visible bar code portion and an invisible code portion using a single detector. The bar code reading system includes light sources for the visible and invisible codes, a detector for alternately detecting the visible light reflected from the authentication mark in response to illumination by the visible light source and the visible light emitted by the authentication mark as a result of fluorescence, and a control unit programmed to process the signals generated at the detector to decode the authentication mark.
Additional objects, features and advantages of the invention will be set forth in the description of preferred embodiments which follows.